/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.spatial.prefix;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.spatial.prefix.tree.Cell;
import org.apache.lucene.spatial.prefix.tree.CellCanPrune;
import org.apache.lucene.spatial.prefix.tree.CellIterator;
import org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree;
import org.apache.lucene.spatial.query.SpatialArgs;
import org.apache.lucene.spatial.query.SpatialOperation;
import org.apache.lucene.spatial.query.UnsupportedSpatialOperation;
import org.locationtech.spatial4j.shape.Shape;

/**
 * A {@link PrefixTreeStrategy} which uses {@link AbstractVisitingPrefixTreeQuery}. This strategy
 * has support for searching non-point shapes (note: not tested). Even a query shape with
 * distErrPct=0 (fully precise to the grid) should have good performance for typical data, unless
 * there is a lot of indexed data coincident with the shape's edge.
 *
 * @lucene.experimental
 */
public class RecursivePrefixTreeStrategy extends PrefixTreeStrategy {
  /*
   * Future potential optimizations:
   *
   * Each shape.relate(otherShape) result could be cached since much of the same relations will be invoked when
   * multiple segments are involved. Do this for "complex" shapes, not cheap ones, and don't cache when disjoint to
   * bbox because it's a cheap calc. This is one advantage TermQueryPrefixTreeStrategy has over RPT.
   *
   */

  protected int prefixGridScanLevel;

  // Formerly known as simplifyIndexedCells. Eventually will be removed. Only compatible with RPT
  // and cells implementing CellCanPrune, otherwise ignored.
  protected boolean pruneLeafyBranches = true;

  protected boolean multiOverlappingIndexedShapes = true;

  public RecursivePrefixTreeStrategy(SpatialPrefixTree grid, String fieldName) {
    super(grid, fieldName);
    prefixGridScanLevel =
        grid.getMaxLevels() - 4; // TODO this default constant is dependent on the prefix grid size
  }

  public int getPrefixGridScanLevel() {
    return prefixGridScanLevel;
  }

  /**
   * Sets the grid level [1-maxLevels] at which indexed terms are scanned brute-force instead of by
   * grid decomposition. By default this is maxLevels - 4. The final level, maxLevels, is always
   * scanned.
   *
   * @param prefixGridScanLevel 1 to maxLevels
   */
  public void setPrefixGridScanLevel(int prefixGridScanLevel) {
    // TODO if negative then subtract from maxlevels
    this.prefixGridScanLevel = prefixGridScanLevel;
  }

  public boolean isMultiOverlappingIndexedShapes() {
    return multiOverlappingIndexedShapes;
  }

  /** See {@link ContainsPrefixTreeQuery#multiOverlappingIndexedShapes}. */
  public void setMultiOverlappingIndexedShapes(boolean multiOverlappingIndexedShapes) {
    this.multiOverlappingIndexedShapes = multiOverlappingIndexedShapes;
  }

  public boolean isPruneLeafyBranches() {
    return pruneLeafyBranches;
  }

  /**
   * An optional hint affecting non-point shapes and tree cells implementing {@link CellCanPrune},
   * otherwise ignored.
   *
   * <p>It will prune away a complete set sibling leaves to their parent (recursively), resulting in
   * ~20-50% fewer indexed cells, and consequently that much less disk and that much faster
   * indexing. So if it's a quad tree and all 4 sub-cells are there marked as a leaf, then they will
   * be removed (pruned) and the parent is marked as a leaf instead. This occurs recursively on up.
   * Unfortunately, the current implementation will buffer all cells to do this, so consider
   * disabling for high precision (low distErrPct) shapes. (default=true)
   */
  public void setPruneLeafyBranches(boolean pruneLeafyBranches) {
    this.pruneLeafyBranches = pruneLeafyBranches;
  }

  @Override
  public String toString() {
    StringBuilder str = new StringBuilder(getClass().getSimpleName()).append('(');
    str.append("SPG:(").append(grid.toString()).append(')');
    if (pointsOnly) str.append(",pointsOnly");
    if (pruneLeafyBranches) str.append(",pruneLeafyBranches");
    if (prefixGridScanLevel != grid.getMaxLevels() - 4)
      str.append(",prefixGridScanLevel:").append(prefixGridScanLevel);
    if (!multiOverlappingIndexedShapes) str.append(",!multiOverlappingIndexedShapes");
    return str.append(')').toString();
  }

  @Override
  protected Iterator<Cell> createCellIteratorToIndex(
      Shape shape, int detailLevel, Iterator<Cell> reuse) {
    if (!pruneLeafyBranches || isGridAlignedShape(shape))
      return super.createCellIteratorToIndex(shape, detailLevel, reuse);

    List<Cell> cells = new ArrayList<>(4096);
    recursiveTraverseAndPrune(grid.getWorldCell(), shape, detailLevel, cells);
    return cells.iterator();
  }

  /** Returns true if cell was added as a leaf. If it wasn't it recursively descends. */
  private boolean recursiveTraverseAndPrune(
      Cell cell, Shape shape, int detailLevel, List<Cell> result) {

    if (cell.getLevel() == detailLevel) {
      cell.setLeaf(); // FYI might already be a leaf
    }
    if (cell.isLeaf()) {
      result.add(cell);
      return true;
    }
    if (cell.getLevel() != 0) {
      result.add(cell);
    }

    int leaves = 0;
    CellIterator subCells = cell.getNextLevelCells(shape);
    while (subCells.hasNext()) {
      Cell subCell = subCells.next();
      if (recursiveTraverseAndPrune(subCell, shape, detailLevel, result)) {
        leaves++;
      }
    }

    if (!(cell instanceof CellCanPrune)) {
      // Cannot prune so return false
      return false;
    }

    // can we prune?
    if (leaves == ((CellCanPrune) cell).getSubCellsSize() && cell.getLevel() != 0) {
      // Optimization: substitute the parent as a leaf instead of adding all
      // children as leaves

      // remove the leaves
      do {
        result.remove(result.size() - 1); // remove last
      } while (--leaves > 0);
      // add cell as the leaf
      cell.setLeaf();
      return true;
    }
    return false;
  }

  @Override
  public Query makeQuery(SpatialArgs args) {
    final SpatialOperation op = args.getOperation();

    Shape shape = args.getShape();
    int detailLevel = grid.getLevelForDistance(args.resolveDistErr(ctx, distErrPct));

    if (op == SpatialOperation.Intersects) {
      if (isGridAlignedShape(args.getShape())) {
        return makeGridShapeIntersectsQuery(args.getShape());
      }
      return new IntersectsPrefixTreeQuery(
          shape, getFieldName(), grid, detailLevel, prefixGridScanLevel);
    } else if (op == SpatialOperation.IsWithin) {
      return new WithinPrefixTreeQuery(
          shape,
          getFieldName(),
          grid,
          detailLevel,
          prefixGridScanLevel,
          -1); // -1 flag is slower but ensures correct results
    } else if (op == SpatialOperation.Contains) {
      return new ContainsPrefixTreeQuery(
          shape, getFieldName(), grid, detailLevel, multiOverlappingIndexedShapes);
    }
    throw new UnsupportedSpatialOperation(op);
  }

  /**
   * A quick check of the shape to see if it is perfectly aligned to a grid. Points always are as
   * they are indivisible. It's okay to return false if the shape actually is aligned; this is an
   * optimization hint.
   */
  protected boolean isGridAlignedShape(Shape shape) {
    return isPointShape(shape);
  }

  /** {@link #makeQuery(SpatialArgs)} specialized for the query being a grid square. */
  protected Query makeGridShapeIntersectsQuery(Shape gridShape) {
    assert isGridAlignedShape(gridShape);
    if (isPointsOnly()) {
      // Awesome; this will be equivalent to a TermQuery.
      Iterator<Cell> cellIterator = grid.getTreeCellIterator(gridShape, grid.getMaxLevels());
      // get last cell
      Cell cell = cellIterator.next();
      while (cellIterator.hasNext()) {
        int prevLevel = cell.getLevel();
        cell = cellIterator.next();
        assert prevLevel < cell.getLevel();
      }
      assert cell.isLeaf();
      return new TermQuery(new Term(getFieldName(), cell.getTokenBytesWithLeaf(null)));
    } else {
      // Well there could be parent cells. But we can reduce the "scan level" which will be slower
      // for a point query.
      // TODO: AVPTQ will still scan the bottom nonetheless; file an issue to eliminate that
      return new IntersectsPrefixTreeQuery(
          gridShape, getFieldName(), grid, getGrid().getMaxLevels(), getGrid().getMaxLevels() + 1);
    }
  }
}
